Elastomer torsion springs have been utilized in a number of different applications; one such torsion spring is disclosed in Kramer et al. U.S. Pat. No. 4,171,920. Specific applications for elastomer torsion springs are quite numerous; among others, they include vehicle shock absorbers, gate closers, and biasing devices (often called tensioners) for conveyor belt scrapers. Some can be set in increments to supply a given torsional force; such devices include the conveyor belt scraper torsion biasing devices (tensioners) disclosed in Gordon U.S. Pat. No. 4,533,036 and in Swinderman et al. U.S. Pat. No. 4,925,434. Continuously adjustable torsion bias devices, suitable for use as tensioners in conveyor belt scrapers or in physical therapy apparatus, are also described in Gordon U.S. Pat. Nos. 5,149,305 and 5,417,407.
Known adjustable elastomer bias devices are usually torsion bias devices; the elastomer that is stressed to provide a bias force is most often in the form of one or two elastomer cylinders, twisted to pre-stress the device. Such devices, as exemplified by those described in the aforementioned Gordon and Swinderman et al. patent documents, are rather limited in the range of available bias force. Thus, to cover all requirements a plurality of different bias devices may be required for a given application, a rather devices may be required for a given application, a rather uneconomic requirement. Moreover, most known elastomer bias devices are not well adapted to use in both torsional and linear bias applications.